Chronic diseases are often expressed by episodic worsening of clinical symptoms. Preventive treatment of chronic diseases reduces the overall dosage of required medication and associated side effects, and lowers mortality and morbidity. Generally, preventive treatment should be initiated or intensified as soon as the earliest clinical symptoms are detected, in order to prevent progression and worsening of the clinical episode and to stop and reverse the pathophysiological process. Therefore, the ability to accurately monitor pre-episodic indicators increases the effectiveness of preventive treatment of chronic diseases.
Many chronic diseases cause systemic changes in vital signs, such as breathing and heartbeat patterns, through a variety of physiological mechanisms. For example, common respiratory disorders, such as asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF), are direct modifiers of breathing and/or heartbeat patterns. Other chronic diseases, such as diabetes, epilepsy, and certain heart conditions (e.g., congestive heart failure (CHF)), are also known to modify cardiac and breathing activity. In the case of certain heart conditions, such modifications typically occur because of pathophysiologies related to fluid retention and general cardiovascular insufficiency. Other signs such as coughing and sleep restlessness are also known to be of importance in some clinical situations.
Many chronic diseases induce systemic effects on vital signs. For example, some chronic diseases interfere with normal breathing and cardiac processes during wakefulness and sleep, causing abnormal breathing and heartbeat patterns.
Breathing and heartbeat patterns may be modified via various direct and indirect physiological mechanisms, resulting in abnormal patterns related to the cause of modification. Some respiratory diseases, such as asthma, and some heart conditions, such as CHF, are direct breathing modifiers. Other metabolic abnormalities, such as hypoglycemia and other neurological pathologies affecting autonomic nervous system activity, are indirect breathing modifiers.
Asthma is a chronic disease with no known cure. Substantial alleviation of asthma symptoms is possible via preventive therapy, such as the use of bronchodilators and anti-inflammatory agents. Asthma management is aimed at improving the quality of life of asthma patients. Asthma management presents a serious challenge to the patient and physician, as preventive therapies require constant monitoring of lung function and corresponding adaptation of medication type and dosage. However, monitoring of lung function is not simple, and requires sophisticated instrumentation and expertise, which are generally not available in the non-clinical or home environment.
Monitoring of lung function is viewed as a major factor in determining an appropriate treatment, as well as in patient follow-up. Preferred therapies are often based on aerosol-type medications to minimize systemic side-effects. The efficacy of aerosol type therapy is highly dependent on patient compliance, which is difficult to assess and maintain, further contributing to the importance of lung-function monitoring.
Asthma episodes usually develop over a period of several days, although they may sometimes seem to appear unexpectedly. The gradual onset of the asthmatic episode provides an opportunity to start countermeasures to stop and reverse the inflammatory process. Early treatment at the pre-episode stage may reduce the clinical episode manifestation considerably, and may even prevent the transition from the pre-clinical stage to a clinical episode altogether.
Two techniques are generally used for asthma monitoring. The first technique, spirometry, evaluates lung function using a spirometer, an instrument that measures the volume of air inhaled and exhaled by the lungs. Airflow dynamics are measured during a forceful, coordinated inhalation and exhalation effort by the patient into a mouthpiece connected via a tube to the spirometer. A peak-flow meter is a simpler device that is similar to the spirometer, and is used in a similar manner. The second technique evaluates lung function by measuring nitric-oxide concentration using a dedicated nitric-oxide monitor. The patient breathes into a mouthpiece connected via a tube to the monitor.
Efficient asthma management requires daily monitoring of respiratory function, which is generally impractical, particularly in non-clinical or home environments. Peak-flow meters and nitric-oxide monitors provide a general indication of the status of lung function. However, these monitoring devices do not possess predictive value, and are used as during-episode markers. In addition, peak-flow meters and nitric-oxide monitors require active participation of the patient, which is difficult to obtain from many children and substantially impossible to obtain from infants.
CHF is a condition in which the heart is weakened and unable to circulate blood to meet the body's needs. The subsequent buildup of fluids in the legs, kidneys, and lungs characterizes the condition as congestive. The weakening may be associated with either the left, right, or both sides of the heart, with different etiologies and treatments associated with each type. In most cases, it is the left side of the heart which fails, so that it is unable to efficiently pump blood to the systemic circulation. The ensuing fluid congestion of the lungs results in changes in respiration, including alterations in rate and/or pattern, accompanied by increased difficulty in breathing and tachypnea.
Quantification of such abnormal breathing provides a basis for assessing CHF progression. For example, Cheyne-Stokes Respiration (CSR) is a breathing pattern characterized by rhythmic oscillation of tidal volume with regularly recurring periods of alternating apnea and hyperpnea. While CSR may be observed in a number of different pathologies (e.g., encephalitis, cerebral circulatory disturbances, and lesions of the bulbar center of respiration), it has also been recognized as an independent risk factor for worsening heart failure and reduced survival in patients with CHF. In CHF, CSR is associated with frequent awakening that fragments sleep, and with concomitant sympathetic activation, both of which may worsen CHF. Other abnormal breathing patterns may involve periodic breathing, prolonged expiration or inspiration, or gradual changes in respiration rate usually leading to tachypnea.
Fetal well-being is generally monitored throughout pregnancy using several sensing modalities, including ultrasonic imaging as a screening tool for genetic and developmental defects and for monitoring fetal growth, as well as fetal heartbeat monitoring using Doppler ultrasound transduction. It has been found that a healthy baby responds to activity by increased heart rate, similar to the way an adult's heart rate changes during activity and rest. Fetal heart rate typically varies between 80 and 250 heartbeats per minute, and accelerates with movement in a normal, healthy fetus. Lack of such variability has been correlated with a high incidence of fetal mortality when observed prenatally. In late stages of pregnancy, particularly in high-risk pregnancies, fetal heartbeat is commonly monitored on a regular basis to monitor fetal well-being and to identify initial signs of fetal distress, which usually result in active initiation of an emergency delivery. Current solutions to monitor fetal well-being are generally not suitable for home environments.
Ballistocardiography is the measurement of the recoil movements of the body which result from motion of the heart and blood in the circulatory system. Transducers are available which are able to detect minute movements of the body produced by the acceleration of the blood as it moves in the circulatory system. For example, U.S. Pat. No. 4,657,025 to Orlando, which is incorporated herein by reference, describes a device for sensing heart and breathing rates in a single transducer. The transducer is an electromagnetic sensor constructed to enhance sensitivity in the vertical direction of vibration produced on a conventional bed by the action of patient's heartbeat and breathing functions, and is described as achieving sufficient sensitivity with no physical coupling between the patient resting in bed and the sensor placed on the bed away from the patient.
Pulsus paradoxus is a physical sign present in a variety of cardiac and extra-cardiac conditions, which is of valuable diagnostic and prognostic significance. Pulsus paradoxus is generally defined as a fall in systolic blood pressure of over 10 mmHg during inspiration. Pulsus paradoxus has been associated with the following conditions: cardiac tamponade, pericardial effusion, constrictive pericarditis, restrictive cardiomyopathy, pulmonary embolism, acute myocardial infarction, cardiogenic shock, bronchial asthma, tension pneumothorax, anaphylactic shock, volvulus of the stomach, diaphragmatic hernia, superior vena cava obstruction. In bronchial asthma, pulsus paradoxus is of significance because it has often been associated with mild obstructions and can therefore serve as an early warning sign. Pulsus paradoxus is generally difficult to assess in children, particularly in an emergency room (see, for example, Brenner B E et al., “The clinical presentation of acute asthma in adults and children,” In Brenner, B E, ed. Emergency Asthma (New York: Marcel Dekker, 1999:201-232)).
U.S. Pat. No. 6,468,234 to Van der Loos et al., which is incorporated herein by reference, describes apparatus for measuring sleep quality that utilizes sensors incorporated in a sheet which is laid on top of a conventional mattress on which the subject sleeps. The sensors can collect information such as the subject's position, temperature, sound/vibration/movement, and optionally other physical properties. The apparatus comprises one or more layers of arrays of integrated sensors, which can be incorporated in layer pads, which is then placed on a conventional mattress; one or more controllers coupled with the arrays of integrated sensors in each layer pad for the purpose of acquiring data from the sensors; real-time analysis software for analyzing data acquired by the controller from the array of integrated sensors; interface software for collecting user lifestyle data; lifestyle correlation software for correlating the lifestyle data with the data acquired by said array of sensors; and one or more active components to improve sleep quality based on the data acquired through the sensors and the lifestyle data. The array of sensors provide one or more of the following data: position, temperature, sound, vibration, and movement data.
U.S. Pat. No. 6,547,743 to Brydon, which is incorporated herein by reference, describes a movement-sensitive mattress having a plurality of independent, like movement sensors for measuring movement at different locations on the mattress to generate a plurality of independent movement signals. The signals are processed to derive respiratory variables including rate, phase, maximum effort or heart rate. Such variables can be combined to derive one or more diagnostic variables including apnea and labored breathing classifications.
U.S. Pat. No. 6,840,907 to Brydon, which is incorporated herein by reference, describes a respiratory analysis system for monitoring a respiratory variable of a patient. The system comprises a sensor array for accommodating a patient to be in contact therewith and a processing means. The array has a plurality of independent like sensors for measuring respiratory movement at different locations on the patient to generate a set of independent respiratory movement signals. The processing means receives and processes the movement signals to derive a classification of individual breaths using, for each breath, the respective phase and/or amplitude of each movement sensor signal within the set for that breath.
U.S. Pat. No. 6,485,441 to Woodward, which is incorporated herein by reference, describes a mattress device including sensors placed in correspondence with a mattress core layer and a mattress top layer of the mattress device, in order to monitor a patient's sleep behavior. The mattress core and top layers provide a static position transmission characteristic and a dynamic impulse transmission characteristic enabling the sensors to recognize body imprint position and body impulses induced by the sleeping patient with a broad bandwidth.
U.S. Pat. No. 5,448,996 to Bellin et al., which is incorporated herein by reference, describes a patient monitor sheet device for measuring respiration, heart beat, and body position. Sensors are located in a bed sheet with which a subject comes in contact. One sensor produces a signal corresponding to respiratory induced, pulmonary motion, and myocardial pumping sounds. A second sensor produces a signal corresponding to changes in body position. A processor amplifies and filters the induced signals to produce an output correlated to respiration rate, heart beat rate, and changes in body position.
U.S. Pat. No. 6,517,497 to Rymut et al., which is incorporated herein by reference, describes techniques for monitoring and/or quantitatively measuring a patient's respiration using a flexible piezoelectric film sensor. The apparatus includes a piezoelectric film which converts acoustical waves generated by the patient's respiration into electrical signals. The piezoelectric film sensor can be used to monitor the respiration of a patient by correlating the sound generated in the patient's airway with respiratory activity. The data generated by the sensor may be further analyzed by a patient monitor to diagnose respiratory conditions.
U.S. Pat. No. 5,002,060 to Nedivi, which is incorporated herein by reference, describes a monitoring system adapted to simultaneously monitor cardiac and respiratory rates and characteristics and substantial changes in temperature of a subject. The system uses sensors which are passive and non-invasive, and located remotely from (i.e., completely off of) the subject. The system is adapted to distinguish the desired signals from undesired environmental noise. The signals are processed in order to provide an alarm accompanied with displayed indication of any irregularities in the cardiac and respiratory rates and characteristics, and substantial changes in temperature. The system also includes a device to transmit said displayed data and alarm to a remote location as desired.
U.S. Pat. No. 6,450,957 to Yoshimi et al., which is incorporated herein by reference, describes a respiration monitoring system that monitors the state of disorder of the respiratory system of a sleeping patient based on the detection of respiratory body movement, without the need to put sensors directly on the patient's body. The system includes weight sensors that produce weight signals attributable to the patient's respiratory body movement. From weight signals having a frequency band of respiration, a respiratory body movement signal is produced. The fall of blood oxygen saturation which occurs during obstructive apnea of the sleeping patient is determined based on the variation pattern of the amplitude of respiratory body movement signal. The occurrence and frequency of the fall of blood oxygen saturation are displayed on a display unit.
U.S. Pat. No. 5,853,005 to Scanlon, which is incorporated herein by reference, describes a transducer in communication with fluid in a pad. The pad is held in close contact against a sound or movement source, and monitors acoustic signals transferred into the fluid. The signal pattern is monitored aurally and/or compared to predetermined reference patterns, and optional control and stimulation means can be activated in response to the comparison results. The sensed acoustic signal can be transmitted to a remote receiver or processed locally. Typically, the acoustic signal is representative of the heartbeat or breathing of a living organism. The monitoring system may be applied to diverse situations including SIDS, apnea, home baby monitoring, medical transport devices, blood pressure cuffs, seats, combat casualty care and hand-held devices. An embodiment is described in which the system is attached to home or institution mattresses for health monitoring, recovery, research, or presence detection.
U.S. Pat. No. 6,666,830 to Lehrman et al., which is incorporated herein by reference, describes a system for detecting the onset of an obstructive sleep apnea event before the obstructive sleep apnea event fully develops, and before the cessation of breathing occurs. The system includes one or more microphones capable of detecting breathing sounds within an airway of a person. The microphones generate signals representative of the breathing sounds, and send the signals to a controller. The controller identifies at least one signal pattern that is associated with a breathing pattern of the person that occurs at the onset of an obstructive sleep apnea event. The controller may also identify at least one signal pattern that is associated with a partially-occluded breathing pattern of the person. The controller identifies the signal patterns by using digital signal processing techniques to analyze the signals representative of breathing sounds. The method involves detecting breathing sounds within an airway of a person, generating signals representative of the breathing sounds, and identifying at least one signal pattern that is associated with a breathing pattern of the person that occurs at the onset of an obstructive sleep apnea event.
U.S. Pat. No. 6,790,183 to Murphy, which is incorporated herein by reference, describes a lung sound diagnostic system for use in collecting, organizing and analyzing lung sounds associated with the inspiration(s) and expiration(s) of a patient. The system includes a plurality of transducers that may be placed at various sites around the patient's chest. The microphones are coupled to signal processing circuitry and A/D converters which digitize the data and preferably provides the digital data to a computer station. The system may also include application programs for detecting and classifying abnormal sounds. The resulting information may be displayed in a variety of formats to facilitate diagnosis. Additionally, the system may include an analysis program for comparing selected criteria corresponding to the detected abnormal sounds with predefined thresholds in order to provide a likely diagnosis. Also described are a system and method for differentiating between the crackles produced by an patient with interstitial pulmonary fibrosis (IPF) from the crackles produced by a CHF patient.
U.S. Pat. No. 6,168,568 to Gavriely, which is incorporated herein by reference, describes a phonopneumograph system for analyzing breath sounds. The system includes a plurality of breath-related sensors placed around the respiratory system of a patient for measuring breath-related activity, and a breath analyzer. The breath analyzer matches the breath sound data produced by the breath-related sensors to a plurality of breath sound templates, each of which parameterizes one type of breath sound, and determines the presence of regular and/or adventitious breath sounds only when the breath sound data matches, within predetermined goodness of fit criteria, one or more of the breath sound templates.
U.S. Pat. No. 6,261,238 to Gavriely, which is incorporated herein by reference, describes a method for analyzing breath sounds produced by a respiratory system. The method includes measuring breath sounds produced by the respiratory system; tentatively identifying a signal as being caused by a breath sound of a given type if it meets a first criterion characteristic of the breath sound of the given type; and confirming the identification if a tentatively identified signal meets a second criterion characteristic of the breath sound of the given type.
U.S. Pat. No. 5,738,102 to Lemelson, which is incorporated herein by reference, describes a system for monitoring and computer analyzing select physiological variables of a patient in real time in order to alert medical personnel to the need for medical treatment or automatically administering such treatment under computer control. Such physiological variables monitored by the system may include lung sounds, respiratory rate and rhythm, heart rate and rhythm, heart sounds, and body temperature. Coded signals relating to the physiological variables are produced and compared with reference versions of same by a decision computer in order to evaluate the patient's condition. If the evaluation indicates medical treatment is needed, the decision computer activates a local and/or a remote alarm to alert medical personnel and/or activates one or more actuators for administering a medical treatment such as the injection or infusion of a drug. Examples of body sounds which may be detected are respiratory sounds and heart sounds. In the case of the former, the computer produces coded signals representing the rate and rhythm of breathing derived from the respiratory sounds. The system is described as being able to detect abnormal breathing patterns such as apnea, tachypnea, hyperpnea (e.g., Kussmaul breathing associated with metabolic acidosis), bradypnea, Cheyne-Stokes breathing, ataxic breathing, and obstructive breathing. Coded signals may also be generated from the respiratory sounds which indicate the presence of added lung sounds such as rales associated with pneumonia and pulmonary edema, wheezes associated with obstructive lung disease, and pleural rubs due to inflammation of the pleural membranes.
US Patent Application Publication 2005/0085866 and PCT Publication WO 05/037366 to Tehrani, which are incorporated herein by reference, describe methods for sensing breathing disorders, irregularities, or insufficiencies. One aspect includes sensing a precursor to an onset of a breathing disorder or episode of a breathing disorder and responding to sensing the precursor. Another aspect includes responding to treat the breathing disorder before manifestation of the disorder. Another aspect includes identifying a likelihood of a breathing disorder and responding using the likelihood and other information indicating onset or occurrence of a breathing disorder. In one embodiment, the breathing disorder event is apnea or the onset of an episode of apnea. In another embodiment, the breathing disorder event is an episode of Cheyne-Stokes respiration.
PCT Publication WO 05/037077 to Tehrani, which is incorporated herein by reference, describes techniques for detecting and managing heart failure patient symptoms. Respiration and/or cardiac parameters are sensed to determine the status of a patient's condition. These symptoms may be classified for appropriate patient disease management. A patient's activity level may be monitored in conjunction with respiration and/or cardiac parameters to provide additional patient status information. Pulmonary edema is one condition that may be determined to exist when a respiration parameter is out of range for a given sensed activity level.
U.S. Pat. No. 6,599,251 to Chen et al., which is incorporated herein by reference, describes non-invasive techniques for monitoring the blood pressure of a subject. A pulse signal is detected at both a first and second location on the subject's body. The elapsed time between the arrival of corresponding points of the pulse signal at the first and second locations is determined. Blood pressure is related to the elapsed time by mathematical relationships.
U.S. Pat. No. 6,290,654 to Karakasoglu, U.S. Pat. No. 6,375,623 to Gavriely, U.S. Pat. No. 6,223,064 to Lynn et al., and US Patent Application Publication 2004/0225226 to Lehrman et al., which are incorporated herein by reference, describe various techniques for detecting and/or analyzing episodes of sleep apnea.
US Patent Application Publication 2004/0133079 to Mazar et al., which is incorporated herein by reference, describes techniques for predicting patient health and patient relative well-being within a patient management system. An embodiment utilizes an implantable medical device comprising an analysis component and a sensing component further comprising a three-dimensional accelerometer, a transthoracic impedance sensor, a cardio-activity sensor, an oxygen saturation sensor, and a blood glucose sensor. One analysis described is detecting changes in transthoracic impedance variation patterns that are indicative of the early occurrence of a new disease state (such as Chronic Obstructive Pulmonary Disease), the onset of an illness (such as asthma), or the progression of a disease (such as DC impedance indicating lung fluid accumulation which corresponds to the progression of heart failure).
U.S. Pat. No. 5,522,382 to Sullivan et al., which is incorporated herein by reference, describes an air flow device for treating upper airway disordered breathing. The airflow device has means for delivering variable pressure levels of breathable air to a patient's respiratory system, and means for controlling the time during which the delivered pressurized air rises from an initial pressure level to a higher operating pressure level.
PCT Publication WO 05/028029 to Stahmann et al., which is incorporated herein by reference, describes techniques for monitoring, diagnosing, and/or treating a patient. The techniques include detecting or predicting events, such as disordered breathing (apnea, hypopnea, tachypnea), coughing and/or breathing irregularities associated with pulmonary diseases and disorders such as asthma, pulmonary edema, chronic obstructive pulmonary disease, and/or pleural effusion. A pre-apnea or pre-hypopnea condition may be detected by analyzing the patient's respiration patterns. Respiration cycles just prior to a disordered breathing event, e.g., an apnea or hypopnea event, may exhibit a characteristic pattern. For example, an apnea event for many patients is preceded by a period of hyperventilation with a number of rapid, deep breaths. The pattern of hyperventilation may be detected by analyzing patient's transthoracic impedance signal to determine respiration rate and tidal volume.
US Patent Application Publication 2005/0043644 to Stahmann et al., which is incorporated herein by reference, describes an approach for predicting disordered breathing by detecting one or more conditions associated with disordered breathing. The detected conditions are compared to disordered breathing prediction criteria. A prediction of disordered breathing is performed based on the comparison of the detected conditions to the prediction criteria. At least one of comparing the detected conditions to the prediction criteria and predicting disordered breathing is performed at least in part using an implantable device.
U.S. Provisional Patent Application 60/504,229 to Stahmann et al., which is incorporated herein by reference, describes techniques for coordinated functioning of a cardiac device and a respiratory device. The cardiac and the respiratory devices operate cooperatively to provide one or more of patient monitoring, diagnosis, and therapy. The system may include a processing system external and coupled to the cardiac and respiratory devices. The processing system may operate cooperatively with the cardiac and respiratory devices to coordinate one or more medical procedures.
U.S. Pat. No. 6,047,203 to Sackner et al., which is incorporated herein by reference, describes a non-invasive physiological signs monitoring device, including a shirt having electrocardiogram electrodes and various inductive plethysmographic sensors. When an adverse condition or other preprogrammed condition occurs, a message is communicated to the patient and/or to a remote receiving unit for monitoring by a health care professional or other machine. For example, if a patient has asthma, pertinent signs such as respiratory drive/ventilation (peak inspiratory flow/ventilation and/or peak inspiratory acceleration/ventilation) may be monitored as non-invasive signs of increasing bronchospasm above a predetermined threshold. This measure is utilized to provide directions to the monitored patient, such as, for example, “You have signs of bronchospasm; please take your aerosol medication now!” If aerosol medication is taken correctly and the proper breathholding pattern is observed, then the output device may state, “Aerosol taken, good!”
US Patent Application Publication 2003/0135127 to Sackner et al., which is incorporated herein by reference, describes physiological monitoring apparel worn by a monitored individual, the apparel having attached sensors for monitoring parameters reflecting pulmonary function, cardiac function, or the function of other organ systems. In an embodiment, an alarm is generated based on a trend progressing over one to a few hours. For example, in a congestive heart failure patient, over two hours of increasing respiratory rate, perhaps coupled with sustained cardiac rate changes, may signal early the onset of pulmonary edema.
U.S. Pat. No. 6,015,388 to Sackner et al., which is incorporated herein by reference, describes a method for measuring respiratory drive, including determining a peak inspiratory flow and a peak inspiratory acceleration from a breath waveform derived from rib cage motion and abdominal motion using a plethysmograph or other external respiratory measuring device. The respiratory drive is described as being ascertainable even during complete blockage of the respiratory system. The peak inspiratory drive is used to initiate inspiration in a mechanical ventilator and for determining an index describing a shape of the waveform for controlling a continuous positive air pressure (CPAP) device.
US Patent Application Publication 2004/0111040 to Ni et al., which is incorporated herein by reference, describes techniques for detecting disordered breathing, including sensing one or more signals associated with disordered breathing indicative of sleep-disordered breathing while the patient is sleeping. Sleep-disordered breathing is detected using the sensed signals associated with disordered breathing. The sensed signals associated with disordered breathing may also be used to acquire a respiration pattern of one or more respiration cycles. Characteristics of the respiration pattern are determined, and the respiration pattern is classified as a disordered breathing episode based on the characteristics of the respiration pattern. One or more processes involved in the detection of disordered breathing are performed using an implantable device.
US Patent Application Publication 2005/0061315 to Lee et al., which is incorporated herein by reference, describes techniques for monitoring one or more patient conditions using a monitoring device that is fully or partially implantable. Feedback information is developed based on the monitored conditions and is provided to a device delivering therapy to treat sleep disordered breathing. Components of the monitoring device are disposed within an implantable housing that is separate from the housing of the therapy device. The therapy device may comprise a housing that is implantable or patient-external. The feedback information may be used to adjust the sleep disordered breathing therapy.
US Patent Application Publication 2003/0004423 to Lavie et al., which is incorporated herein by reference, describes techniques for monitoring the sleep state condition of an individual using an external probe applied to a peripheral body location, such as the individual's finger or toe, for detecting changes in the peripheral vascular bed volume of the individual. Such information is described as being useful for diagnosing and/or treating a number of sleep disorders, as well as other conditions, such as impotence, diabetes, and various disorders in children. For example, Cheyne-Stokes breathing may be detected using a finger-probe, or nocturnal asthmatic activity may be recognized.
U.S. Pat. No. 6,512,949 to Combs et al., which is incorporated herein by reference, describes an impedance monitor for discerning edema through evaluation of respiratory rate.
U.S. Pat. No. 6,454,719 to Greenhut, which is incorporated herein by reference, describes techniques for determining the cardiac condition of a patient by a cardiac monitor apparatus using a respiration parameter such as a current respiration signal or a respiration rate. The variability of the respiration parameter is used to generate a signal indicative of the current heart failure status of the patient, and, more particularly, whether the patient's condition has improved, worsened, or remained unchanged over a predetermined time period. The circuitry for detecting the respiration parameter may be implanted in the patient, for example as part of a pacemaker, while at least some of the analyzing circuitry may be external and remote from the patient. Alternatively the whole device may be implantable.
U.S. Pat. No. 6,600,949 to Turcott, which is incorporated herein by reference, describes a method for monitoring the condition of a heart failure patient using respiration patterns. An implantable or other ambulatory monitor senses the patient's respiratory patterns to identify the presence of periodic breathing or Cheyne-Stokes respiration. In a first embodiment, mechanical changes of the thorax due to breathing are detected and this data is used to recognize hyperventilation and apnea or hypoventilation. In a second embodiment, Cheyne-Stokes respiration is recognized by detecting changes in blood or tissue pH or CO2 concentration and partial pressure. In another embodiment, changes in pulse amplitude associated with Cheyne-Stokes respiration are detected. Alternating loss and return of respiration-induced amplitude modulation or pulse-interval variation may also be used to identify the presence of Cheyne-Stokes respiration. In yet another embodiment, modulation of the average heart rate over time is monitored and its absence is used as an indicator of Cheyne-Stokes respiration. This information may be used to warn the patient or healthcare provider of changes in the patient's condition warranting attention.
U.S. Pat. No. 6,527,729 to Turcott, which is incorporated herein by reference, describes a method for monitoring the progression of disease of a heart failure patient. An implantable or other ambulatory monitor senses acoustic signals including heart and lung sounds within the patient. Significant changes in the energy content of either the heart or lung sounds is indicative of a heart failure exacerbation. This information may be used to warn the patient or healthcare providers of changes in the patient's condition warranting attention.
U.S. Pat. No. 6,641,542 to Cho et al., which is incorporated herein by reference, describes apparatus for detecting and treating sleep respiratory events, including a plurality of sensors gathering physiological data related to sleep respiratory events. A processor extracts an average cycle length and a frequency of at least one of Cheyne-Stokes respiration and periodic breathing based upon the physiological data, and determines whether therapy is required based on the average cycle length and the frequency.
U.S. Pat. No. 6,830,548 to Bonnet et al., which is incorporated herein by reference, describes apparatus for diagnosing a patient respiratory profile. The apparatus measures respiratory activity and delivers a signal representative of the periodicity and amplitude of the successive respiratory cycles of the patient, in particular, a minute ventilation signal. The device analyzes the signal and discriminates between various types of respiratory profiles, in particular Cheyne-Stokes breathing.
U.S. Pat. No. 6,589,188 to Street et al., which is incorporated herein by reference, describes a method for detecting and monitoring periodic breathing to provide an indication of changes in the hemodynamic status of a heart failure patient. The method includes monitoring at least one of four independent physiologic parameters: respiratory tidal volume, respiratory rate (B-B interval), arterial oxygen saturation, and heart rate (R-R interval). These parameters may be analyzed by performing power spectral analysis or thresholding/binning. Each analysis method can be applied to each measure or combination thereof. In a preferred embodiment, the patient is monitored when at rest or asleep to prevent interference from activity-related respiratory variations.
U.S. Pat. No. 5,902,250 to Verrier et al., which is incorporated herein by reference, describes a method for determining the sleep state of a patient, including monitoring heart rate variability of the patient and determining sleep state based on the heart rate variability. Also described is a method for determining respiratory pattern, including monitoring heart rate variability by receiving heart beat signals and determining respiratory pattern from the strength of the signals. A home-based, wearable, self-contained system determines sleep-state and respiratory pattern, and assesses cardiorespiratory risk of a patient based on the frequency of eyelid movements, the frequency of head movements, and heart rate variability of the patient. The system includes an automatic alarm system for awakening a patient should a dangerous breathing or heart-related event occur. The system is described as being particularly useful for patients in heart failure, particularly those with an existing respiratory disorder, a combination which may provoke Cheyne-Stokes respiration.
U.S. Pat. No. 5,590,650 to Genova, which is incorporated herein by reference, describes apparatus for monitoring physiological vital signs of a human body without physically contacting the body. The apparatus includes a sensor for transforming a movement and/or acoustical wave produced by the body into an electrical signal, and a signal processor coupled to the sensor for receiving the electrical signal from the sensor, and for processing the electrical signal adaptively using wavelet correlator analysis. Typically, the apparatus is used to monitor heart rate, respiration rate and related sounds, digestive system sounds, as well as other physiological vital signs.
U.S. Pat. No. 6,893,404 to Ragnarsdottir, which is incorporated herein by reference, describes techniques for measuring breathing movements and determining breathing patterns, by measuring the simultaneous movement of a plurality of points of a human subject, such that a breathing pattern may be determined based on data obtained in a single acquisition.
U.S. Pat. No. 6,752,766 to Kowallik et al., which is incorporated herein by reference, describes a method for identifying a minimum of one breathing parameter which is characteristic of the breathing status of a sleeping individual. The method comprises: measuring the derivative trend with respect to time of a minimum of one variable of state of the cardiovascular system of the individual, which variable recurrently changes with the respiration; determining breath-to-breath intervals, each of which represents the duration of one breath, from the results of the measurement; and identifying the breathing parameter which is defined by the variability of the breath-to-breath intervals in phases of unobstructed breathing and/or statistical variables derived therefrom.
U.S. Pat. No. 6,368,287 to Hadas, which is incorporated herein by reference, describes a device, described as suitable for use without professional medical supervision, for screening for sleep apnea. All elements of the device are housed in a small, flexible, plastic housing which is placed on the user's philtrum. A thermistor acquires data describing the respiratory pattern. A processor analyzes the respiratory pattern in real time and outputs a study result, describing the occurrence of any episodes of apnea.
U.S. Pat. No. 6,375,621 to Sullivan, which is incorporated herein by reference, describes apparatus that monitors the acoustic and electromechanical signals of a patient, and calculates an energy spectrum periodogram or histogram using time series analysis techniques. The patient lies down on a large piezoelectric film (a few microns thick) that has the capability of measuring signals from very high to very low frequencies. The heart and respiration rates as well as obstructive apnea can be observed, detected and measured from the spectral peaks in the resulting energy spectrum. An alarm calls for assistance in the event of an apnea, including obstructive apnea, or a Sudden Infant Death Syndrome (SIDS) episode.
U.S. Pat. No. 5,964,720 to Pelz, which is incorporated herein by reference, describes a system for the monitoring of a patient's physiological condition, including a measuring device for measuring the mechanical activity of a patient's body, including a module for detecting mechanical vibrations and transmitting them to a sensing element for converting the mechanical movements into electric signals. Also described is a device for transmitting the electric signals for processing the electric signals and separating from them cardiac, respiration, and body movement signals. Further described is a device for measuring a pulse wave propagation rate. Still further described is a device for determining characteristics and derived parameters of cardiac and respiratory cycles, as well as for storing and displaying the data. Additionally described is a comparator for comparing parameters of data with predetermined parameters, and a device for actuating an alarm signal when signals of the data exceed a preset range.
U.S. Pat. No. 6,239,706 to Yoshiike et al., which is incorporated herein by reference, describes an in-bed state detection system including a load detection section for detecting a load applied to a bed and providing a corresponding load signal; a determination section for determining an in-bed state based on the load signal; and a transmission section for transmitting a result of the determination.
U.S. Pat. No. 5,879,313 to Raviv et al., which is incorporated herein by reference, describes a method for classifying respiratory sounds, including selecting a first set of respiratory sounds, manually determining a classification content of the first set of respiratory events, and extrapolating the classification content of the first set of respiratory events to an at least second set of respiratory events.
U.S. Pat. No. 6,064,910 to Andersson et al., which is incorporated herein by reference, describes a device for determining the respiration rate and/or respiration depth of a patient, including a sensor for sensing heart sounds, and an analyzer for analyzing the variation of the amplitude of the sensed heart sounds to determine the respiration rate and/or respiration depth from this amplitude variation. Apparatus for monitoring the respiration of a patient includes such a device and the analyzer is arranged to determine an anomaly in the amplitude variation of the sensed heart sounds as an indication of a respiration anomaly.
U.S. Pat. No. 6,126,595 to Amano et al., which is incorporated herein by reference, describes a device for diagnosing physiological state based on blood pulse waves detected in the body. The device includes a blood pulse wave detector and stroke-volume-per-beat measurer, which respectively detect blood pulse wave and stroke volume in the body; a blood pulse wave extraction memory, which extracts characteristic information from the detected blood pulse wave; and an output portion which outputs an alarm.
U.S. Pat. No. 5,520,176 to Cohen, which is incorporated herein by reference, describes a sleep analysis system for analyzing a sleep episode of a subject based on measured values of a plurality of parameters characterizing that subject. Portions of the measured parameter signals are classified as significant events, and the significant events are segregated based on parameter signal criteria and time correlation as a basis for the analysis.
U.S. Pat. No. 5,944,680 to Christopherson et al., which is incorporated herein by reference, describes a method of predicting critical points in patient respiration, including monitoring at least one characteristic of a respiratory effort waveform of a patient to detect a respiratory event.
U.S. Pat. No. 6,033,370 to Reinbold et al., which is incorporated herein by reference, describes a capacitive force sensor which has a plurality of layers forming a force sensing detector, the detector providing a signal in response to pressure; a feedback element that provides feedback in response to the signal from the force sensing detector; and a housing for encompassing the force sensing detector and the feedback element.
U.S. Pat. No. 6,135,970 to Kadhiresan et al., which is incorporated herein by reference, describes techniques for assessing the status of well-being of patients being treated for CHF using cardiac pacing as a therapy. By sampling the output from an activity sensor or the like, and by noting the frequency with which the averaged rectified sensor output exceeds a preset threshold following changes in the pacing mode, the efficacy of the new mode compared to the previous one can be evaluated.
U.S. Pat. No. 6,751,498 to Greenberg et al., which is incorporated herein by reference, describes techniques for fetal heart and maternal heart and uterine monitoring. The techniques acquire biopotential waveforms indicative of the mother's heart beat from sensors located at or near the mother's chest, and waveforms indicative of the combined maternal and fetal heart beats from abdominal sensors located on the mother's abdomen, lower back, or both. The signals from the abdominal sensors are divided into a plurality of channels. An adaptive signal processing filter (ASPF) algorithm or other suitable algorithm is then used to cancel the estimated maternal waveform from each channel derived from the abdominal sensors. The system then selects from the resulting waveforms at least one waveform to serve as the reference fetal waveform. The reference waveform is then processed against the other abdominal waveforms preferably using the ASPF algorithm again to form an enhanced fetal signal that is a representation of the fetus's biopotential electrocardiogram (ECG). The fetus's biopotential ECG is subsequently be used to measure fetal heart rate and other biophysical profile parameters. Surface electromyogram (EMG) signals are described as allowing for concurrent monitoring of uterine contractions and afford improved cancellation of motion artifacts.
US Patent Application Publication 2004/0210155 to Takemura et al., which is incorporated herein by reference, describes a monitoring device for detecting conditions of a sleeping person. The device comprises multiple independent distance sensors installed facing different positions in a monitored target area to be monitored, for measuring a distance to a monitored target; a calculating unit for calculating changes over time in the outputs of the distance sensors; and a detection processor for detecting changes in shape of the monitored target based on the calculated changes over time in one or multiple distance sensor among the multiple distance sensors.
The following patents and patent application publication, all of which are incorporated herein by reference, may also be of interest:
U.S. Pat. No. 4,657,026 to Tagg;
U.S. Pat. No. 5,235,989 to Zomer;
U.S. Pat. No. 5,957,861 to Combs;
U.S. Pat. No. 6,383,142 to Gavriely;
U.S. Pat. No. 6,436,057 to Goldsmith et al.; and
U.S. Pat. No. 6,856,141 to Ariav.
An article by Shochat M et al., entitled, “PedemaTOR: Innovative method for detecting pulmonary edema at the pre-clinical stage,” undated, available at http://www.isramed.info/rsmm_rabinovich/pedemator.htm, which is incorporated herein by reference, describes an impedance monitor for pre-clinical detection of pulmonary edema. The impedance monitor measures “internal thoracic impedance,” which is roughly equal to lung impedance, by automatically calculating skin-electrode impedance and subtracting it from the measured transthoracic impedance.
It has been suggested that bio-modification of breathing and heart rate might prove beneficial for chronic conditions such as asthma and CHF, as well as for other conditions such as stress (see, for example, U.S. Pat. Nos. 5,076,281, 5,800,337, and 6,090,037 to Gavish, U.S. Pat. No. 6,662,032 to Gavish et al., and US Patent Application Publication 2004/0116784 to Gavish, all of which are incorporated herein by reference). Such bio-modification has been attempted using biofeedback techniques based on continuous measurement and providing visual/auditory feedback related to the magnitude of the monitored parameters.
Some researchers believe that optimal awakening occurs if an individual is awakened during light or REM sleep, rather than during deep sleep stages. For example, Axon Sleep Research Laboratories (Providence, R.I., USA) is developing an intelligent alarm clock (called “SleepSmart”) that monitors sleep cycles and attempts to awaken the user at an optimal point in the sleep cycle. SleepSmart requires the user to sleep with a headband that measures physiological data. It has also been suggested that sleep staging can be obtained from respiration and heart rate information during sleep (see, for example, Shinar Z et al., “Identification of arousals using heart rate beat-to-beat variability,” Sleep 21(3 Suppl): 294 (1998), which is incorporated herein by reference).
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The inclusion of the foregoing references in this Background section does not imply that they constitute prior art or analogous art with respect to the invention disclosed herein.